Update DNS Server Information on Linux CentOS 7

To update the DNS server that the operating system will refer to, please follow below easy steps

1. Edit /etc/resolv.conf. In this example I use nano text editor. If you do not have nano, you can install it by running "yum install nano -y"
# nano /etc/resolv.conf

2. Type in "nameserver" followed by a space, and followed by your DNS server ip address. Please remember that the sequence of the entry is important. So please put your primary DNS server on top of your secondary server in the /etc/resolv.conf. In this example, my primary DNS is 192.168.1.1 and my secondary DNS is 192.168.1.2
nameserver 192.168.1.1
nameserver 192.168.1.2

3. Save and exit. For nano, you can simply press Ctrl-x, y and Enter.

4. Check if you have added the configuration correctly
# cat /etc/resolv.conf
nameserver 192.168.1.1
nameserver 192.168.1.2 

Update Proxmox Network Configuration Without Restarting

In proxmox 6.1-7, if you make any changes to network configuration using the web interface, you either have to reboot the box, or press the "Apply Configuration" button to apply the changes. But the "Apply Configuration" button needs a package named ifupdown2 from proxmox repository to operate correctly.

So in order to make the button usable, so that we do not have to reboot the box every time we change proxmox network configuration, please follow below simple steps

1. Enable pve no-subscription repository, and disable proxmox default enterprise repository by referring here

2. Update proxmox package information
# apt update

3. Install ifupdown2
# apt install ifupdown2 -y

4. Now you can change any network settings in the proxmox web ui, and apply the configuration by pressing "Apply Configuration" button like below

Using Openvpn Client in Alpine Linux

Installing openvpn client in alpine linux is very easy. Just follow below command

# apk add openvpn

To use it, just run the command against an openvpn configuration file

# openvpn myopenvpnconfig.file

The first time you are using openvpn client, you will probably get this error:

ERROR: Cannot open TUN/TAP dev /dev/net/tun: No such file or directory (errno=2)

What you can do is just give 666 permission to /dev/net/tun

# chmod 666 /dev/net/tun

and rerun the openvpn command

# openvpn myopenvpnconfig.file

Once you get this message "Initialization Sequence Completed", you should be able to access your remote server